1. Field of the Invention
This invention relates to an optical axis adjusting device of a vehicle lamp in which an optical axis of illumination light can be adjusted from the outside of a lamp housing of the vehicle lamp.
2. Description of the Prior Art
An optical axis adjusting device is known as shown in FIG. 7. In FIG. 7, reference numerals 1 and 2 designate a lamp housing of a vehicle lamp and a lens closing an opening of the lamp housing, respectively. The lamp housing 1 is made of synthetic resin. A lighting chamber 3 is defined by the lamp housing 1 and the lens 2. A reflector 4 holding a bulb (not shown) is disposed in the lighting chamber 3. An optical axis adjusting mechanism 5 causes the reflector 4 to tilt, thereby changing the direction of an optical axis of the bulb. The optical axis adjusting mechanism 5 is constructed as follows.
A supporting portion 1c and a supporting projection 1b which juts out toward the lighting chamber 3 are formed on the inner surface of a rear wall 1a of the housing 1. A cylindrical guide 1d is formed along the outer surface of the rear wall 1a of the housing 1. The supporting portion 1c is disposed at the lower part of the housing 1 than the supporting projection 1b. In the housing, another supporting portion, which is a pair to the supporting portion 1c, is formed at an interval in the lateral direction of a vehicle body. The supporting portions may be disposed at the upper part of the housing 1. A positional relationship between the supporting projection 1b and the supporting portions 1c is known in the art. A spherical hollow 1e is formed in the supporting projection 1b. The spherical hollow 1e is opened via a conical opening 1f. A pillar 4a facing the conical opening 1f is formed on the rear surface of the reflector 4 integrally with the reflector 4. Likewise, a holding tube 4b facing the supporting portion 1c is formed on the rear surface of the reflector 4 integrally therewith. A joint member 6 is laid between the pillar 4a and the supporting projection 1b. The joint member 6 comprises a spherical part 6a and a screw thread part 6b. The spherical part 6a is movably fitted into the spherical hollow 1e, and the thread part 6b is engaged with a corresponding thread part of the pillar 4a. An ball-like screw nut 7 is mounted in the tube 4b. An aiming screw 8 is rotatably laid between the tube 4b and the supporting portion 1c. The tip part 8a of the aiming screw 8 has threads, and the head part 8b thereof juts out of the rear wall 1a of the housing 1. The thread part 8a is engaged with the ball-like screw nut 7, and the head part 8b is provided with a metallic drive gear 9 fixedly.
A tool D, such as a screwdriver, is guided by the guide 1d so that the tip of the tool D is engaged with a tooth 9a of the drive gear 9. The rotation of the tool D in the above state leads to the rotation of the drive gear 9, thereby leading to the rotation of the aiming screw 8. Accordingly, the ball-like screw nut 7 is moved in the direction of the axis of the aiming screw 8 relatively with respect to the thread part 8a of the aiming screw 8. Accordingly, the reflector 4 is tilted on the spherical part 6a of the joint member 6 so as to adjust the optical axis of the bulb.
In the conventional optical axis adjusting device, the tool D receives reaction force caused by the rotation of the drive gear 9 in a direction in which the tool D and the tooth 9a are separated from each other. Therefore, the tip of the tool D becomes unsteady, and the aiming screw 8 cannot be easily rotated in a state in which the tip of the tool D is tightly engaged with the tooth 9a. In addition, due to the reaction force, the tool D is inclined with respect to an axis (direction in which the tool D is guided) of the guide 1d and, therefore, part of the tool D is strongly pushed against the inner wall of the guide 1d. Disadvantageously, the rotation of the tool D under this state brings about abrasion or crack of the inner wall of the guide 1d.
Further, in the conventional optical axis adjusting device, when the tool D is inserted into the guide 1d, the tip of the tool D cannot be wholly viewed and cannot be quickly placed in proper position. Therefore, the tool D is excessively or insufficiently pushed into the guide 1d. If insufficiently, the tip of the tool D is loosely engaged with the tooth 9a. The rotation of the tool D under the state of loose engagement often brings about deformation of the tooth 9a. On the other hand, if excessively, not only the tooth 9a but also the drive gear 9 itself might be broken.
Further, if the drive gear 9 is made of synthetic resin for the purpose of reduction in weight and cost, the tip of the tool D might break the tooth 9a because of the incomplete engagement of the tip with the tooth 9a when rotated.
It is therefore a first object of the present invention to provide an optical axis adjusting device of a vehicle lamp in which the tip of a tool and a toothed part of a drive gear are certainly engaged with each other when an optical axis of the lamp is adjusted.
It is a second object of the present invention to provide an optical axis adjusting device of a vehicle lamp in which synthetic resin can be used for an optical axis adjusting mechanism.
It is a third object of the present invention to provide an optical axis adjusting device of a vehicle lamp in which the tip of the tool is easily positioned when inserted.
Other objects of the present invention will be appreciated from the embodiments described hereinafter.